In vehicles that include an internal combustion engine, compression braking occurs when the vehicle is coasting. Compression braking is a negative torque supplied by the engine that slows the vehicle down when the accelerator pedal is released. Compression braking can be caused by, for example, a closed-throttle partial-vacuum when there is zero acceleration request.
Hybrid electric vehicles (HEVs) include an internal combustion engine and an electric machine (such as a motor/generator) that provide power to propel the vehicle. If the engine “on” and available to immediate propulsion power, compression braking can be provided by the engine during vehicle coasting. Due to the presence of the electric machine in the powertrain, inconsistencies of compression braking may be felt by an operator of the vehicle during vehicle coasting.